1. Field of the Invention
The present invention relates generally to an optical fiber array, and in particular, to an optical fiber array module including a light emitting device and an optical fiber array.
2. Description of the Related Art
Optical fiber arrays are composed of a plurality of optical fibers arranged in parallel. Each optical fiber is an optical transmission medium and can selectively include a protection layer of a resin substance, which is coated on the outer surface of the plurality of optical fibers. The protection layer is used to fix the plurality of optical fibers. Optical fiber array modules structure aligns an optical fiber array and a light emitting device. A side view light emitting diode (LED) is conventionally used as the light emitting device. Such an optical fiber array module is used as a backlight to illuminate key tops of a portable terminal.
FIG. 1 is a plan view of a conventional optical fiber array module 100. FIG. 2 is a perspective view of a side view LED 110 illustrated in FIG. 1. Referring to FIGS. 1 and 2, the optical fiber array module 100 includes the side view LED 110 for generating light and an optical fiber array 120 coupling a light beam 116 emitted from the side view LED 110 therein.
The side view LED 110 includes a rectangular type window 114 on one side surface 112 thereof. The side view LED 110 emits the light beam 116 having a pre-set divergence angle from the window 114. A horizontal width W1 (hereinafter, width) of the window 114 is 1.9 mm, and a vertical width (hereinafter, length) of the window 114 is 0.46 mm.
The optical fiber array 120 is composed of 28-core plastic optical fibers 122. Each optical fiber is an optical transmission medium and is arranged in parallel. The optical fiber array 120 can also selectively include a protection layer of a resin substance, which is coated on the outer surface of the 28-core plastic optical fibers 122, to fix the 28-core plastic optical fibers 122. Each of the 28-core plastic optical fibers 122 includes a core and a clad. The core has a high refractive index in which light travels with total reflection. The clad has a low refractive index and surrounds the core. The width W3 of the optical fiber array 120 is 7 mm, and the diameter W2 of each of the 28-core plastic optical fibers 122 is 0.25 mm.
For efficient optical coupling, it is preferable to minimize the distance between the window 114 of the side view LED 110 and an end portion of the optical fiber array 120. However, since the width W1 of the window 114 is narrower than the width W3 of the optical fiber array 120 and the divergence angle of the side view LED 110 is narrow, reduction of the distance is limited.
A technique of widening a divergence angle of an LED using a grating has been disclosed. However, luminance distribution of light is not uniform within the widened divergence angle. Thus, in practice, an effective divergence angle for obtaining uniform luminance is not changed. In addition, optical coupling efficiency is low, since the distance between a window of the LED and an end portion of an optical fiber array is still large.
As described above, in conventional optical fiber array modules, luminance of light coupled to the optical fiber array is low, since the distance between a window of an LED and an end portion of an optical fiber array must be more than several or tens mm.
Thus, there is a need in the art for an optical fiber array module for maximizing optical coupling efficiency by minimizing the distance between a window of an LED and an end portion of an optical fiber array.